diff --git a/metrics/lib/json.bash b/metrics/lib/json.bash
index 1eb617b..1641836 100644
--- a/metrics/lib/json.bash
+++ b/metrics/lib/json.bash
@@ -69,7 +69,7 @@ EOF
 
 	local json="$(cat << EOF
 	"test" : {
-		"runtime": "${RUNTIME}",
+		"runtime": "${RUNTIME:-default}",
 		"testname": "${TEST_NAME}"
 	}
 EOF